Douglas Philips wrote:
> On 2007 Mar 20, at 3:30 PM, Dan Weston indited:
>>> I looked up John Backus on wikipedia and followed a link to ALGOL:
>>http://en.wikipedia.org/wiki/ALGOL_60>> where the following "undesirable" property of call-by-name is mentioned.
>>>> "ALGOL 60 allowed for two evaluation strategies for parameter passing:
>> the common call-by-value, and call-by-name. Call-by-name had certain
>> limitations in contrast to call-by-reference, making it an undesirable
>> feature in language design. For example, it is impossible in ALGOL 60
>> to develop a procedure that will swap the values of two parameters if
>> the actual parameters that are passed in are an integer variable and
>> an array that is indexed by that same integer variable. However,
>> call-by-name is still beloved of ALGOL implementors for the
>> interesting thunks that are used to implement it."
>>>> I suppose that call-by-name is still beloved of Haskell implementors
>> as well?
>> Notice that the "problem" with call-by-name is when side-effects are
> involved. In a pure-functional-environment those "problems" don't arise...
>> --Doug
It was the phrase "making it an undesirable feature in language design"
that jumped out at me. Here "language" is an implicitly universally
quantified variable, and the phrase beta-reduces to "call-by-name is an
undesirable feature in Haskell design".